Short Answer TypeState with reason any two possible consequences of elimination of decomposers
from the Earth.
Energy flow in a food chain is unidirectional. Justify this statement. Explain how the pesticides enter a food chain and subsequently get into our body.
Write one difference between asexual and sexual mode of reproduction. Which species is likely to have better chances of survival - the one reproducing asexually or the one reproducing sexually? Justify your answer.
What is the effect of DNA copying, which is not perfectly accurate, on the reproduction process? How does the amount of DNA remain constant though each new generation in a combination of DNA copies of two individuals?
List three main factors responsible for the speciation and briefly describe each one of them.
A trait may be inherited, but may not be expressed. Justify this statement with the help of a suitable example
Long Answer TypeList two reasons for carbon forming a large number of compounds. Name the type of bonding found in most of its compounds. Why does carbon form compounds mainly by this kind of bonding? Give a reason why the carbon compounds.
(i) Generally, have low melting and boiling points.
(ii) do not conduct electricity in the molten state.
(a) List the parts of the human eye that control the amount of light entering into it.
Explain how they perform this function.
(b) Write the function of retina in human eye.
(c) Do you know that the corneal-impairment can be cured by replacing the defective cornea with the cornea of the donated eye? How and why should we organise groups to motivate the community members to donate their eyes after death?
a) The amount of light entering the eyes of a human is controlled by iris and pupil.
The iris automatically adjusts the size of the pupil according to the intensity of light received by the eye.
If the amount of light received by the eye is large (as during the daytime), then the iris contracts the pupil (makes the pupil small) and reduces the amount of light entering the eye. On the other hand, if the amount of light received by the eye is small (as in a dark room or during night), the iris expands the pupil (makes the pupil large) so that more light may enter the eyes. Thus, the iris regulates (or controls) the amount of light entering the eye by changing the size of the pupil.
b) The retina acts as a screen on which the image is formed in the eye.
The retina has a large number of light-sensitive cells called rods and cons. When the image falls on the retina then these light-sensitive cells get activated and generate electrical signals.
c) Yes.
There is a need for awareness among various communities about eye donation after death as it will help a person suffering from an eye ailment to get the treatment.
The following steps can be taken to organize groups to motivate them:
(i) The person who is taking the initiative can communicate with people and after realizing people who are like minded should gather them and form an awareness group.
(ii) The group should then approach various communities and organizations in their area and promote their campaign.
(iii) They can also approach various hospitals and clinics to promote the campaign.
(a) Explain the following terms related to spherical lenses:
(i) optical centre
(ii) centres of curvature
(iii) principal axis
(iv) aperture
(v) principal focus
(vi) focal length
(b) A converging lens has focal length of 12 cm. Calculate at what distance the object should be placed from the lens so that it forms an image at 48 cm on the other side of the lens.
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